| Hippophae Fructus is the dried,ripe berries of Hippophae rhamnoides L.(sea buckthorn),family Elaeagnaceae,It is used as a medicinal herb by Mongolians and Tibetans.Hippophae Fructus has the functions of strengthening the spleen and speeding up the digestion,stopping coughing and dispersing blood stasis,etc.It is used to treat spleen deficiency,cough,phlegm and chest pains and others.H.rhamnoides is widely distributed in Eurasia,and is abundant in China,where it is found in vast areas from northeast and north China to northwest China.Hippophae Fructus is a traditional medicine for many nationalities at home and abroad,with a long history of application,and in recent years has also been widely used in food and cosmetics.As a dual-use item,the quality of sea buckthorn berries has an important influence on the efficacy of downstream products,but systematic quality evaluation studies are still lacking.In this thesis,the influence of drying methods on the quality of sea buckthorn berries and the quality differences between berries of different origins and varieties were evaluated from multiple perspectives using UPLC-DAD,UPLC-PDA-Q/TOF-MS and GC-MS techniques.The details of the study and the results are as follows:1.Firstly,total polyphenol and total flavonoid contents of different samples were determined by the Folin-Ciocalteu method and the NaNO2-Al(NO3)3-NaOH method,respectively.The results showed that:(1)the vacuum freeze-drying method could retain total polyphenols and total flavonoids in sea buckthorn to the maximum extent.(2)Total flavonoid content and total polyphenol content of large berry cultivars of sea buckthorn were significantly lower than those of H.rhamnoides ssp.sinensis,and the former was not suitable for use as a medicinal herb.(3)The total polyphenol and total flavonoid content of sea buckthorn berries from Xinjiang was significantly lower than that of sea buckthorn berries from other origins;while sea buckthorn berries from Lanxian,Shanxi and Chifeng,Inner Mongolia had the highest content.2.The variation of phenolic acids and flavonoids in sea buckthorn berries was further investigated using the UPLC-DAD method.A method for the simultaneous quantification of 2 phenolic acids and 10 flavonoids in sea buckthorn was successfully established.The method was applied to 21 batches of sea buckthorn berries from 13 regions,as a result,a characteristic profile of sea buckthorn was established with six characteristic peaks.Meanwhile,the results of the content determination indicated that:(1)the components with high content in sea buckthorn were narcissin,isorhamnetin-3-O-glucoside and rutin.Most of these compounds were highest in the freeze-dried sea buckthorn berries.Conversely,the content of protocatechu ic acid increased after hot-air drying,sun-drying and shade-drying treatments.(2)The total content of the 12 phenolic compounds in freeze-dried berries was 1.16 to 1.63 times higher than in other dried berries.The order of the total content of the 12 compounds in large berry cultivars of sea buckthorn was:hot air-dried>shade-dried>sun-dried.In contrast,the order of the total phenolic compounds in H.rhamnoides ssp.sinensis:sun-dried≈shade-dried>hot air-dried.(3)H.rhamnoides from Xinjiang contained more procyanic acid,gallic acid,quercetin and isorhamnetin.3.UPLC-PDA-Q/TOF-MS was used to identify 41 compounds in Hippophae Fructus,including 4 phenolic acids,3 catechin derivatives and 34 flavonol glycosides,of which isorhamnetin glycosides were the main flavonol glycosides.UPLC-UV combined with multivariate statistical analysis showed that there were differences in the chemical composition of sea buckthorn berries treated with the four drying methods,but sun-dried and shade-dried berries was more similar.The content of narcissin and isorhamnetin-3-Oglucoside was susceptible to different drying methods and different species and could be used as potential markers for quality evaluation of sea buckthorn berries.Metabolomic data from 21 batches of sea buckthorn from different origins indicated that the chemical composition of large berry cultivars of sea buckthorn was different from that of H.rhamnoides ssp.sinensis,so the two should be properly differentiated for research and production use.H.rhamnoides ssp.turkestanica from Xinjiang and H.rhamnoides ssp.sinensis from Shanxi,Inner Mongolia,Hebei and Tibet had different secondary metabolites.A total of 21 different compounds were obtained by OPLS-DA analysis for large berry cultivars of sea buckthorn,H.rhamnoides ssp.turkestanica from Xinjiang and H.rhamnoides ssp.sinensis from other origins,they were identified as flavonoids,phenolic acids and triterpene saponins,which may be characteristic markers to be used for quality evaluation.4.In addition to polar and semi-polar compounds,the lipids of sea buckthorn is also important.Firstly,the parameters for the extraction of sea buckthorn berries oil by supercritical fluid extraction(SFE-CO2)were optimised by orthogonal experiments.The results showed that the best extraction was achieved at an extraction temperature of 40℃,a pressure of 350 bar and an extraction time of 80 min.The oil was extracted from 11 sea buckthorn berries under optimal conditions and the content of 10 fatty acids was determined by GC-MS.The results showed that the oil yield and fatty acid content of large berry cultivars of sea buckthorn were much higher than those of H.rhamnoides ssp.sinensis,and the highest oil content was obtained from "SQ3" from Xinjiang.This study provides preliminary data on the oil yield and fatty acid content of sea buckthorn berries,which can be used as an indicator for quality evaluation.5.The antioxidant activities of different sea buckthorn samples were determined using three in vitro antioxidant assays(DPPH,ABTS and FRAP methods),and the antioxidant activities of 12 compounds in berries were investigated by UPLC-DPPH method.The results showed that:(1)The order of antioxidant activity was:freeze-drying>shadedrying>hot-air drying or sun-drying,indicating that high temperature and light would destroy the active compounds in sea buckthorn berries.(2)The antioxidant activity of large berry cultivars of sea buckthorn was much lower than that of H.rhamnoides ssp.sinensis.(3)The antioxidant activity of H.rhamnoides ssp.sinensis from Xinjiang was much lower than that from other origins,and the best sea buckthorn produced from Lanxian County,Shanxi,Chifeng City,Inner Mongolia,Limin Town,Shanxi and Luqu County,Qinghai.(4)The contribution of gallic acid,quercetin and isorhamnetin to the antioxidant activity of sea buckthorn berries was greater.The antioxidant capacity of phenolic acids and flavonoids depends on the phenolic hydroxyl groups,the more phenolic hydroxyl groups,the better the activity of the compounds.In summary,this thesis systematically investigated the effects of different drying methods,varieties and origins on the phenolic and fatty acid components of sea buckthorn and evaluated their antioxidant activities.It was found that vacuum freeze-drying was the most suitable drying method for sea buckthorn;that large berry cultivars of sea buckthorn was not suitable as a raw material for medicinal herbs;and that H.rhamnoides ssp.sinensis from Lanxian,Shanxi and Chifeng,Inner Mongolia had high phenolic content and good antioxidant activity.The thesis also established a characteristic profile of sea buckthorn and selected markers that cause differences in sea buckthorn quality,which can be used for identification and effective differentiation of sea buckthorn samples of different qualities.The results of the study provide a reference for improving and upgrading the quality evaluation criteria of sea buckthorn herbs and are of great significance in guiding the further development and utilization of sea buckthorn resources. |
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